<html>
  <head></head>
  <body>
    <div id="app">
      <div>Proxy</div>
    </div>
  </body>
  <script src="./proxy.js"></script>
  <script>
    let product = reactive({ price: 5, quantity: 2, rate: { value: 0.9 } })
    let total = 0

    effect(() => {
      total = product.price * product.quantity * product.rate.value
    })
  </script>
</html>
